The Three Sisters planting method is a traditional agricultural practice used by Native Peoples where corn, beans, and squash are planted in a symbiotic triad to enhance soil fertility and plant growth. Graphic by Grace Rodgers/USFWS Text of graphic Three Sisters Planting The Three Sisters Planting is a traditional agricultural practice used by Native Peoples where corn, beans, and squash are planted in a symbiotic triad to enhance soil fertility and plant growth. Corn -- provides a structure for climbing bean vines to reach sunlight. Beans -- fertilize the corn and squash by releasing beneficial nitrogen into the soil. Squash -- broad, spiny leaves prevent weeds, shade the soil to hold moisture, and protect the other plants against predators. Credit: U.S. Fish & Wildlife Service